© ISO 2012 Water quality — Sampling — Part 3 Preservation and handling of water samples Qualité de l’eau — Ėchantillonnage — Partie 3 Conservation et la manipulation des échantillions d’eau INTERNATIO[.]
Solids
5.1.1 Sodium thiosulfate pentahydrate, Na 2 S 2 O 3 ã5H 2 O, w(Na 2 S 2 O 3 ã5H 2 O) > 99 %.
5.1.4 Sodium tetraborate decahydrate, Na 2 B 4 O 7 ã10H 2 O, w(Na 2 B 4 O 7 ã10H 2 O), > 99 %.
CAUTION Sodium tetraborate decahydrate is known to be a carcinogen, mutagen and reproductive toxin (CMR).
Solutions
Dissolve 10,0 g of zinc acetate in ∼100 ml of water Dilute to 100 ml with water Store the solution in a polypropylene or glass bottle for a maximum period of 1 a.
5.2.2 Orthophosphoric acid (ρ ≈ 1,7 g/ml), H 3 PO 4 , w(H 3 PO 4 ) > 85 %, c(H 3 PO 4 ) = 15 mol/l.
5.2.3 Hydrochloric acid (ρ ≈ 1,2 g/ml), HCl, w(HCl) > 36 %, c(HCl) = 12,0 mol/l.
5.2.4 Nitric acid (ρ ≈ 1,42 g/ml), HNO 3 , w(HNO 3 ) > 65 %, c(HNO 3 ) = 15,8 mol/l.
5.2.5 Sulfuric acid (ρ ≈ 1,84 g/ml), H2SO4 (freshly prepared).
Dilute concentrated sulfuric acid (H2SO4), ρ ≈ 1,84 g/ml, w(H2SO4) ≈ 98 % 1 + 1 by carefully adding the concentrated acid to an equal volume of water and mix.
WARNING — Adding the concentrated acid to the water can give violent reactions because of an exothermic reaction.
5.2.6 Sodium hydroxide solution (ρ ≈ 0,40 g/ml), NaOH.
5.2.7 Formaldehyde solution (formalin), CH 2 O, ϕ(CH 2 O) = 37 % to 40 % (freshly prepared),
WARNING — Beware of formaldehyde vapours Do not store large numbers of samples in small work areas.
5.2.8 Disodium salt of ethylenediaminetetraacetic acid (EDTA) (ρ ≈ 0,025 g/ml),
Dissolve 25 g EDTA in 1 000 ml of water.
5.2.10 Alkaline Lugol’s solution, 100 g potassium iodide (5.1.6), 50 g iodine (5.1.7), and 250 g sodium acetate (5.1.8) in 1 000 ml water to pH 10.
5.2.11 Acidic Lugol’s solution, 100 g potassium iodide (5.1.6), 50 g iodine (5.1.7) and 100 ml glacial acetic acid (5.2.17) in 1 000 ml water to pH 2.
5.2.12 Neutralized formaldehyde solution, formaldehyde solution (5.2.7) neutralized with sodium tetraborate (5.1.4) or hexamethylenetetramine (5.1.5) Formalin solution at 100 g/l gives a final solution of ϕ(CH2O) = 3,7 % to 4,0 %.
WARNING — Beware of formaldehyde vapours Do not store large numbers of samples in small work areas.
Ethanol (5.2.9), formaldehyde solution (5.2.7) and glycerol (5.2.18) (100 + 2 + 1 parts by volume, respectively).
5.2.14 Sodium hypochlorite NaOCl, w(NaOCl) = 10 % Dissolve 100 g sodium hypochlorite (NaOCl) in
5.2.15 Potassium iodate KIO3, w(KIO3) = 10 % Dissolve 100 g potassium iodate (KIO3) in 1 000 ml of water.
5.2.16 Methanoic acid (formic acid) CH 2 O 2 , ϕ(CH 2 O 2 ) > 98 %.
Materials
5.3.1 Container and cap, types as specified in Tables A.1 to A.3.
5.3.2 Filter, pore size 0,40 àm to 0,45 àm, unless a different filter size is specified in the analytical
Container selection and preparation
The choice of sample container (5.3.1) is of major importance and ISO 5667-1 provides some guidance on this subject.
Sample containers shall be made of a material appropriate for preserving the natural properties of both the sample and the expected range of contaminants Suitable types of containers for each analyte to be measured are given in Tables A.1 to A.3.
NOTE For very low concentrations of metals, containers prescribed can be different from those used for higher concentrations Details can be found in Table A.1 or in the analytical International Standards.
If the samples are to be frozen, suitable containers, such as polyethylene (PE) or polytetrafluoroethylene (PTFE), shall be used to prevent breakage.
The use of disposables is preferred Some manufacturers supply containers with a certificate of cleanliness If such a certificate of cleanliness is supplied, it is not necessary to clean or rinse the containers before use.
Filtration on site
Filtration on site is required in some cases.
— Groundwaters shall be filtered on site if dissolved metals need to be analysed.
— Waters shall be filtered (5.3.2) on site, if this is required according to Annex A Unless specified otherwise, a filter pore size 0,40 àm to 0,45 àm shall be used.
If immediate filtration on site is impossible, then the reason and the time between sampling and filtration shall be added to the test report.
Filling the container
The container (5.3.1) shall be filled completely unless prescribed differently in Tables A.1 to A.3 or the analytical International Standard used If the samples are to be frozen as part of their preservation, sample containers shall not be completely filled This is in order to prevent breakage which may arise from expansion of ice during the freezing and thawing process.
If no preservatives are present in the bottle, then prerinsing the bottle may be advisable Guidance on prerinsing can be found in ISO 5667-14.
Sample handling and preservation for physical and chemical examination
Waters, particularly fresh waters, waste waters and groundwaters, are susceptible to changes as a result of physical, chemical or biological reactions which may take place between the time of sampling and the commencement of analysis The nature and rate of these reactions are often such that, if precautions are not taken during sampling, transport and storage (for specific analytes), the concentrations determined are different to those existing at the time of sampling.
The extent of these changes is dependent on the chemical and biological nature of the sample, its temperature, its exposure to light, the type of the container in which it is placed, the time between sampling and analysis, and the conditions to which it is subjected, e.g agitation during transport Further specific causes of variation are listed in a) to f). a) The presence of bacteria, algae and other organisms can consume certain constituents of the samples These organisms can also modify the nature of the constituents to produce new constituents This biological activity affects, for example, the concentrations of dissolved oxygen, carbon dioxide, compounds of nitrogen, phosphorus and, sometimes, silicon. b) Certain compounds can be oxidized either by dissolved oxygen present in the samples, or by atmospheric oxygen [e.g organic compounds, Fe(II) and sulfides]. c) Certain substances can precipitate out of solution, e.g calcium carbonate, metals, and metallic compounds such as Al(OH)3, or can be lost to the vapour phase (e.g oxygen, cyanides, and mercury). d) Absorption of carbon dioxide from air can modify pH, conductivity, and the concentration of dissolved carbon dioxide Passage of compounds like ammonia and silicon fluoride through some types of plastics may also affect pH or conductivity. e) Dissolved metals or metals in a colloidal state, as well as certain organic compounds, can be irreversibly adsorbed on to the surface of the containers or solid materials in the samples. f) Polymerized products can depolymerize, and conversely, simple compounds can polymerize.
Changes to particular constituents vary both in degree and rate, not only as a function of the type of water, but also, for the same water type, as a function of seasonal conditions.
These changes are often sufficiently rapid to modify the sample considerably in a short time In all cases, it is essential to take precautions to minimize these reactions and, in the case of many analytes, to analyse the sample with a minimum of delay If the required precaution for changes is filtration on site, then a filter (5.3.2) shall be used.
Details of the sample preservation are given in Table A.1.
Sample handling and preservation for biological examination
The handling of samples for biological examination is different from that for samples requiring chemical analysis The addition of chemicals to the sample for biological examination can be used for either fixation and/or preservation of the sample The term “fixation” is defined as the protection of morphological structures, while the term “preservation” is defined as the protection of organic matter from biochemical or chemical degradation Preservatives, by definition, are toxic, and the addition of preservatives may lead to the death of living organisms Prior to death, irritation may cause the most delicate organisms, which do not have strong cell walls, to collapse before fixation is complete To minimize this effect, it is important that the fixation agent enter the cell quickly.
IMPORTANT Acidic Lugol’s solutions (5.2.11) can lead to the loss of structures in organisms or also lead to the loss of small organisms (e.g some flagellates); in this case, use an alkaline Lugol’s solution (5.2.10), e.g during the summer, when the appearance of silico-flagellates is frequently observed.
The fixing and/or preservation of samples for biological examination shall meet the following criteria: a) the effect of the fixative, and/or preservative, on the loss of the organism shall be known beforehand; b) the fixative or preservative shall effectively prevent the biological degradation of organic matter at least during the storage period of the samples; c) the fixative, and/or preservative, shall enable the biological analyte (e.g organisms or taxonomical groups) to be assessed during the storage period of the samples.
Details of the preservation of samples are given in Table A.2.
Sample handling and preservation for radiochemical analysis
WARNING — Radioprotection such as shielding may be necessary, depending on the activity of the sample.
There is little difference between the handling of samples for radiochemical analysis and the handling of samples for physicochemical analysis.
The delay between sampling and measurement has to be consistent with the radioactive half-life of the radionuclides of interest The conditions to be taken for adequate storage are independent of the radioactive half-life, but identical to those required for the corresponding stable isotope.
NOTE Cooling radiological samples is primarily used to prevent algal growth and biological spoilage It is not a necessary preservation step for radiochemical analyses These samples are often combined with those for physical, chemical or biological analysis.
Cooling or freezing procedures shall be applied to samples to increase the time period available for transport and storage and if required by Tables A.1 to A.3 When transport takes place, the sampling plan (e.g ISO 5667-1) shall consider:
— the time between sampling and start of transport;
— starting time of analysis in the laboratory.
This sum of these three periods is limited to the maximum storage times according to Tables A.1 to A.3.
If the maximum storage time cannot be met, then the sampling plan shall be reformulated to allow these requirements to be accommodated.
A cooling temperature of the device during transport of (5 ± 3) °C has been found suitable for many applications Cooling and freezing procedures applied shall be in line with instructions from the analytical laboratory Freezing especially requires detailed control of the freezing and thawing process in order to return the sample to its initial equilibrium after thawing.
Containers holding samples shall be protected and sealed during transport in such a way that the samples do not deteriorate or lose any part of their content Container packaging shall protect the containers from possible external contamination, particularly near the opening, and should not itself be a source of contamination.
Glass containers shall be protected from potential breakage during transport by appropriate packaging Samples shall be transported as soon as possible after sampling and with cooling if necessary according to Tables A.1 to A.3.
Laboratory samples for dispatch or transport by third parties and preserved laboratory samples should be sealed in such manner that the integrity of the sample can be maintained.
Samples required for (potential) regulatory investigations should be sealed to a level that meets the requirements of the authorities or other organization(s) concerned with the transport of the sample.
During transportation samples shall be stored in a cooling device capable of maintaining a temperature of (5 ± 3) °C For proper evaluation of the conditions during transport a device capable of recording the (maximum) temperature of the air surrounding the sample may be used.
NOTE Devices capable of logging of the air temperature during the transportation are available, but their use and adequate calibration can be costly.
Container labels should withstand wetting, drying and freezing without detaching or becoming illegible The labelling system shall be waterproof to allow use on site.
The exact information given in the sampling report and on the sample labels depends on the objectives of the particular measurement programme In all cases, an indelible label shall be secured to the sample container.For each sample, at least the following information shall be available.
— date, time and location of sampling;
— details of sample preservation, or fixation used;
— details of sample storage used;
— any information regarding integrity and manipulation of the sample;
— any other information, as necessary.
A unique identifier, traceable to sample date, location, and sample number shall appear on the label of the sample container.
All other information is supplementary and should be detailed in the sample report.
All information regarding sample, handling and storage shall be included in a sampling report.
Laboratory staff shall receive and check information on sample preservation and sample transport conditions.
In all cases, and especially when a “chain of custody” process needs to be established, the number of sample containers received in the laboratory shall be verified against the number of sample containers submitted.
The storage duration of the water samples within the laboratory is specific to the analyte(s) to be analysed Samples shall be stored no longer than the maximum storage period given in Tables A.1 to A.3 The maximum storage time includes the time of transport to the laboratory (3.4).
The refrigeration conditions within the laboratory shall be (3 ± 2) °C Where samples are frozen for preservation, unless otherwise specified, the temperature shall be maintained below −18 °C Exceptions to these refrigeration conditions are listed in Tables A.1 to A.3.
When thawing frozen samples it is recommended that each sample container be placed in a separate secondary container to minimize the risk of liquid loss, should a split become apparent during the thawing process or a rupture occur during initial freezing and storage A mild impact can cause splitting of some plastics at low temperatures.
With respect to thawing, it is recommended that this be done under ambient conditions, unless specified otherwise in Tables A.1 to A.3 or the analytical International Standard being used.
This part of ISO 5667 and the analytical International Standards listed in this annex are complementary See the Notice on page 1.
In some cases the alternative preservation techniques listed contradict each other It is intended that where an existing analytical International Standard is used, the preservation technique described in that method applies However, alternative preservation techniques given in this part of ISO 5667 can also be appropriate Where no preservation method is described in the analytical International Standard, or no analytical International Standard is used, the technique(s) listed in this part of ISO 5667 shall be used.
A validation protocol used for validation studies can be found in Annex C Reports and data regarding validation are listed in the bibliography.
FEP perfluoro(ethylene/propylene) PFA perfluoroalkoxy (polymer)
PE-HD high density polyethylene PTFE polytetrafluoroethylene
PET polyethylene terephthalate PVC poly(vinyl chloride)
See Table A.1 The following general remarks should be noted in relation to use of Table A.1.
— A preservation time of 1 d means that if 24 h is exceeded, this should be stated in the report.
— The types of containers are identical to those in the analytical International Standards In some cases, the type of container in the standard is very specific, e.g PTFE This is essential when very low concentrations have to be measured In other cases, when the specific type of plastic is not important, the term plastics is sufficient.
The following general remarks should be noted in relation to use of Table A.2.
— Plastics used for containers in the laboratory are for instance PE, PTFE, PET, PP, PFA, and FEP.
— lf a preservation period is not specified, it is generally unimportant The indication “1 month” represents preservations without particular difficulty.
The following general remarks should be noted in relation to use of Table A.3.
WARNING — Radioprotection such as shielding may be necessary, depending on the activity of the sample.
— Acidification is carried out to avoid algal growth, biological spoilage, and adsorption of metal ions to the inner wall of the sample container.
— Contamination of the sample should be avoided, especially if the sample activity is very low Some sample sites can have measurable activity in the soil or air, or in waters other than those being sampled Laboratories, as well as some items of domestic equipment, can contain radioactive material When sampling precipitation, any special requirements in this table are additional to those given in ISO 5667-8 As the collection of sufficient sample can require a period of days, both the starting and finishing times and dates should be recorded A record of precipitation collection for the sample station for the appropriate period should be appended Stabilizer or carrier may be added, if appropriate for the analytes being measured.